In systems for distributing still image data and video data through TV broadcasting or through networks, generally, a scrambling process is performed to the image data to allow people who satisfy predetermined conditions to access the image data.
For example, there exists a method in which a distributing side performs a scrambling process for a partial exchange of the image data to be distributed and then an encoding process, and distributes the image data, while a receiving side performs a decoding process first, and then a descrambling process to the partially exchanged image to display the reconstructed image data.
There exists another method for displaying reconstructed image data in which a distributing side performs an encoding process first, and then scrambling process to image data to be distributed, while a receiving side performs a descrambling process first, and then a decoding process to the scrambled and encoded data.
Such a scrambling process is effective to restrict access to image data or the like, and any fraudulent use of the data can be prevented by issuing a key for a descrambling process only to the authorized users who are permitted to use the data.    Patent Citation 1: U.S. Pat. No. 6,246,777